Method and Device for Controlling Vibrations of a Metallurgical Vessel

ABSTRACT

In a method and a device for controlling vibrations of a metallurgical vessel that occur while gas is being injected into liquid molten metal located in the metallurgical vessel, a certain total amount of gas per unit of time is injected into the liquid molten metal, and the total amount of gas being is injected into the liquid molten metal through a number of individual nozzles in the metallurgical vessel, measured values correlating with the vibrations of the metallurgical vessel occurring are being measured during the injection, wherein while keeping the total amount of gas injected per unit of time largely constant, the amount of gas injected from individual nozzles per unit of time is changed in dependence on the measured values that are measured and correlate with the vibrations of the metallurgical vessel occurring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/EP2009/064720 filed Nov. 6, 2009, which designatesthe United States of America, and claims priority to AustrianApplication No. A2013/2008 filed Dec. 23, 2008, the contents of whichare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The invention relates to a method and a device for controllingvibrations of a metallurgical vessel that occur while gas is beinginjected from nozzles into liquid molten metal located in themetallurgical vessel.

BACKGROUND

In particular in the case of AOD (argon oxygen decarburization)converters used for producing stainless steel, large amounts of gas areintroduced into the liquid molten material of the crude steel vianozzles. As a result, on the one hand the partial pressure of gases inthe molten material can be influenced, on the other hand a bath flow isproduced in the molten material by the injected gas bubbles rising up.This flow leads to a desired intermixing of the molten material.However, the rising gas bubbles lead to a randomly fluctuatingdisplacement of the centre of gravity of the converter filled withliquid molten material, causing the converter to vibrate. Parts of theplant that are connected directly or indirectly to theconverter—particularly those that are rigidly connected to theconverter—may also be made to vibrate by the vibrations of theconverter. Vibrations put a severe load on the converter and the partsof the plant connected to it, such as for example the gear mechanismprovided for tilting the converter and the suspension thereof, and maylead to premature wear or rupture. The foundation on which the converterand associated parts of the plant are located, such as the gearmechanism for example, also undergo oscillations. These may have adamaging effect on the foundation itself and the surroundings thereof.

It is known from US20080047396 to monitor and control the intermixing ofa liquid molten metal by means of gas injection from under-bath nozzlesin such a way that the vibrations of the metallurgical vessel aremeasured. The measurement result is an indication of the quality of theintermixing. On the basis of the measurement result, the total amount ofgas injected per unit of time, the blowing rate, is changed to achieveoptimum intermixing. However, reducing the blowing rate with respect tovalues fixed in a blowing plan is synonymous with extending thetap-to-tap time, and consequently with reducing the productivity of themetallurgical vessel. Moreover, a change of the blowing rate may alsoinfluence the metallurgical properties of the product.

SUMMARY

According to various embodiments, a method and a device for controllingvibrations of a metallurgical vessel occurring during the injection ofgas into the metallurgical vessel filled with a liquid molten metal canbe provided that allow the vibrations of the metallurgical vessel to becontrolled while largely retaining the blowing rate.

According to an embodiment, in a method for controlling vibrations of ametallurgical vessel occurring during the injection of gas into themetallurgical vessel filled with liquid molten metal, a certain totalamount of gas per unit of time being injected into the liquid moltenmetal, and the total amount of gas being injected into the liquid moltenmetal through a number of individual nozzles in the metallurgicalvessel, and measured values correlating with the vibrations of themetallurgical vessel occurring being measured during the injection,wherein, while keeping the total amount of gas injected per unit of timelargely constant, the amount of gas injected from individual nozzles perunit of time is changed in dependence on the measured values that aremeasured and correlate with the vibrations of the metallurgical vesseloccurring.

According to a further embodiment, at least for one of the individualnozzles, preferably two or more of them, the amount of gas injected fromthem per unit of time can be changed, at least for a time, in dependenceon measured values correlating with the vibrations of the metallurgicalvessel occurring. According to a further embodiment, the changing of theintensity of at least one measured value correlating with the vibrationsof the metallurgical vessel occurring that can be brought about bychanging the amount of gas injected from an individual nozzle per unitof time is traced, and the changing of the amount of gas injected froman individual nozzle per unit of time is carried out until the at leastone measured value correlating with the vibrations of the metallurgicalvessel occurring reaches a prescribed value or until the gas flow fromthe nozzle reaches a prescribed maximum or minimum. According to afurther embodiment, the measured values correlating with the vibrationsof the metallurgical vessel occurring can be filtered and digitallyprocessed before they are used for changing the amount of gas injectedfrom the individual nozzles per unit of time. According to a furtherembodiment, when measuring the measured values correlating with thevibrations of the metallurgical vessel occurring, frequencies and/orintensities of vibrations can be determined. According to a furtherembodiment, the measured values correlating with the vibrations of themetallurgical vessel occurring may correlate with vibrations of themetallurgical vessel that have frequencies between 0.1 Hertz and 100Hertz, preferably between 0.2 Hertz and 20 Hertz. According to a furtherembodiment, the measured values, correlating with the vibrations of themetallurgical vessel occurring, in dependence on which the amount of gasintroduced from individual nozzles per unit of time is changed maycorrelate with vibrations of the metallurgical vessel of frequenciesthat lie between 0.2 Hertz and 20 Hertz.

According to another embodiment, a device for controlling vibrations ofa metallurgical vessel occurring during the injection of gas into themetallurgical vessel filled with liquid molten metal and provided with anumber of individual nozzles for the injection of gas, the individualnozzles being respectively connected to a gas feed line of their own,may have at least one sensor for measured values correlating with thevibrations of the metallurgical vessel occurring, and a processing unitfor processing the measured values measured by the sensor, wherein in atleast two gas feed lines there is at least one device for changing thegas flow through the gas feed line, and each device for changing the gasflow is connected to the processing unit.

According to a further embodiment of the device, the device for changingthe gas flow through the gas feed line may allow a continuous changingof the gas flow. According to a further embodiment of the device, thedevice for changing the gas flow through the gas feed line can be adevice for changing the gas flow in stages. According to a furtherembodiment of the device, the sensor for measured values correlatingwith the vibrations of the metallurgical vessel occurring can be avibration sensor. According to a further embodiment of the device, thevibration sensor can be a torque measurement, a strain gage, a positionpickup, a velocity pickup or an acceleration pickup.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below on the basis of schematic figures,which represent embodiments.

FIG. 1 and FIG. 2 show a device according to various embodiments with aconverter having under-bath nozzles.

FIG. 3 shows a device according to various embodiments with a converterhaving under-bath nozzles and nozzles on the side wall of the converter,a number of sensors being respectively arranged at various locations.

DETAILED DESCRIPTION

According to various embodiments, in a method for controlling vibrationsof a metallurgical vessel occurring during the injection of gas into themetallurgical vessel filled with liquid molten metal,

a certain total amount of gas per unit of time is injected into theliquid molten metal,

and the total amount of gas is injected into the liquid molten metalthrough a number of individual nozzles in the metallurgical vessel,

and measured values correlating with the vibrations of the metallurgicalvessel occurring are measured during the injection,

wherein,

while keeping the total amount of gas injected per unit of time largelyconstant, the amount of gas injected from individual nozzles per unit oftime is changed in dependence on the measured values that are measuredand correlate with the vibrations of the metallurgical vessel occurring.

The amount of gas injected from individual nozzles per unit of time ischanged in dependence on the measured values that are measured andcorrelate with the vibrations of the metallurgical vessel occurring. Asa result, the intermixing of the liquid molten metal, andcorrespondingly the centre of gravity of the metallurgical vessel filledwith liquid molten metal, changes. It is correspondingly possible toachieve the effect that vibrations are increased or reduced. As aresult, it is possible to keep parts of the plant that are connecteddirectly or indirectly to the metallurgical vessel—in the case of aconverter, for example, essentially the suspension, support, balingring, tilting drive, gear mechanism and foundation—free from harmfulvibration frequencies or to reduce the intensity of vibrations withharmful frequencies. As a result, the mechanical stressing of theseparts of the plant is reduced. Lower mechanical stressing, andaccompanying longer lifetimes, of the parts of the plant increase theproductivity of the metallurgical vessel.

Measured values correlating with the vibrations of the metallurgicalvessel occurring should be understood as meaning measured values thatallow a quantifiable conclusion to be reached as to the vibrations ofthe metallurgical vessel occurring. Measured values for the vibrationsof the metallurgical vessel are also included by the term “measuredvalues correlating with the vibrations of the metallurgical vesseloccurring”. The measured values correlating with the vibrations of themetallurgical vessel occurring are, for example,

-   -   frequencies and/or intensities of vibrations of the        metallurgical vessel, and/or    -   frequencies and/or intensities of vibrations of parts of the        plant connected directly or indirectly to the metallurgical        vessel.

If directly or indirectly connected parts of the plant are made tovibrate by vibrations of the metallurgical vessel occurring, thesevibrations correlate with the vibrations of the metallurgical vessel ina way that allows the vibrations of the metallurgical vessel to beconcluded from the measurement of these vibrations of the parts of theplant. Such conclusions may be made possible, for example, by measuringat the same time

-   -   vibrations of the metallurgical vessel occurring, and    -   measured values correlating with the vibrations of the        metallurgical vessel occurring, and by determining the        correlation, that is to say the interrelationship, between them.        Knowledge of the correlation determined in this way then allows        the vibrations of the metallurgical vessel to be concluded from        the measured values.

Parts of the plant connected directly to the metallurgical vessel shouldbe understood as meaning parts of the plant that are connected straightto the metallurgical vessel. Parts of the plant connected indirectly tothe metallurgical vessel should be understood as meaning parts of theplant that are connected to the metallurgical vessel via a part of theplant or a number of parts of the plant—that is to say indirectly.

Keeping the total amount of gas injected per unit of time, that is theblowing rate, largely constant, makes it possible for the productivityand the metallurgical properties of the product to be kept largelyconstant.

It is known to a person skilled in the art that, in industrialapplication, the blowing rate cannot be kept constant entirely exactly,but that the actual value fluctuates about a prescribed value over time.For the purposes of the present invention, keeping largely constantshould be understood as meaning that the actual value fluctuates about aprescribed value over time by +/−5%.

The metallurgical vessel may be any type of process vessel for liquidmolten metals, preferably for molten crude steel or molten pig iron,that is to say for example converters, ladles, crucibles or electric arcfurnaces. A tiltable converter is preferred.

The metallurgical vessel has nozzles for injecting gas into the spaceenclosed by the vessel. The arrangement of the nozzles is in this casechosen such that, during the operation of the metallurgical vessel, theylie below the level of the liquid molten metal in the metallurgicalvessel; such nozzles are also known as under-bath nozzles.Correspondingly, during operation, gas is injected into the liquidmolten metal through these nozzles. The nozzles may be arranged in thebottom or the side walls of the metallurgical vessel. The nozzles arepreferably under-bath nozzles arranged in the side walls of themetallurgical vessel.

The measurement during injection of the measured values correlating withthe vibrations of the metallurgical vessel occurring is performed eithercontinuously or at certain time intervals. A continuous measurement hasthe advantage of providing information at all times as to the currentstatus of the vibrations, but involves a considerable data processingeffort. A measurement at certain time intervals has the advantage overcontinuous measurement that the data processing effort is reduced onaccount of the lower amount of measurement data generated. However, itonly provides information about the status of the vibrations at selectedpoints in time.

According to one embodiment of the method, at least for one of theindividual nozzles, preferably two or more of them, the amount of gasinjected from them per unit of time is changed, at least for a time, independence on measured values correlating with the vibrations of themetallurgical vessel occurring.

The aim here should be to maintain for such a nozzle a gas flow throughthe nozzle at all times, in order not to risk any infiltrations ofliquid molten metal into the nozzle and consequently caused damage tothe nozzle. Therefore, complete switching-off of the gas flow throughthe nozzle should be avoided. The greater the number of individualnozzles for which the amount of gas injected from them per unit of timeis changed, the more finely balanced the control of the vibrations ofthe metallurgical vessel can be.

The changing of the amount of gas injected per unit of time may beperformed in stages or continuously. In the case of changing in stages,changes are made between setting stages predetermined on the basis ofthe process engineering conditions. Continuous changing offers theadvantage over changing in stages that a more finely balanced control ofthe vibrations of the metallurgical vessel is possible, and is thereforepreferred.

It is at the same time preferred that the changing of at least onemeasured value correlating with the vibrations of the metallurgicalvessel occurring that is brought about by changing the amount of gasinjected from an individual nozzle per unit of time is traced, and thechanging of the amount of gas injected from an individual nozzle perunit of time is carried out until the at least one measured valuecorrelating with the vibrations of the metallurgical vessel occurringreaches a prescribed value or until the gas flow from the nozzle reachesa prescribed maximum or minimum. The maximum or minimum is prescribed onthe basis of process engineering specifications for the liquid moltenmetal that is actually to be treated. The prescribed value for the atleast one measured value correlating with the vibrations of themetallurgical vessel occurring is dependent on the extent to which thevibrations of the metallurgical vessel are to be controlled.

Since the two variants, changing by stages and continuous changing,should be used at least for a time, mixed forms of them are alsopossible. For example, the amount of gas injected per unit of time mayfirst be changed in stages and then, to make better fine settingpossible, changed continuously. Or it is first changed continuously andthen in stages.

According to a preferred embodiment of the method, the measured valuescorrelating with the vibrations of the metallurgical vessel occurringare filtered and digitally processed before they are used for changingthe amount of gas injected from the individual nozzles per unit of time.This makes it possible to trace more accurately the variation of certainvibrations of the metallurgical vessel, for example those known to beparticularly disruptive.

According to a preferred embodiment, when measuring the measured valuescorrelating with the vibrations of the metallurgical vessel occurring,frequencies and/or intensities of vibrations are determined.

According to one embodiment, the measured values correlating with thevibrations of the metallurgical vessel occurring correlate withvibrations of the metallurgical vessel that have frequencies between 0.1and 100 Hertz, preferably between 0.2 Hertz and 20 Hertz. The values 0.1Hertz and 100 Hertz are included here. Frequencies above 100 Hertzscarcely have any potential to be disruptive.

According to a further embodiment, the measured values, correlating withthe vibrations of the metallurgical vessel occurring, in dependence onwhich the amount of gas introduced from individual nozzles per unit oftime is changed correlate with vibrations of the metallurgical vessel offrequencies that lie between 0.2 Hertz and 20 Hertz. These frequenciesshould be monitored particularly closely, since they have the greatestpotential for causing damage.

The frequencies and intensities of the vibrations of the metallurgicalvessel are measured by means of a vibration sensor or a number ofvibration sensors, it being possible for the measuring principle to bebased, for example, on torque measurement, acceleration measurement,strain gages, position pickups or velocity pickups.

Acceleration pickups, strain gages or position pickups are preferablyused, since they are inexpensive and can be fitted with little effort.

According to further embodiments, a device for carrying out the methodaccording to various embodiments can be provided.

It is a device for controlling vibrations of a metallurgical vesseloccurring during the injection of gas into the metallurgical vesselfilled with liquid molten metal and provided with a number of individualnozzles for the injection of gas, the individual nozzles beingrespectively connected to a gas feed line of their own,

with at least one sensor for measured values correlating with thevibrations of the metallurgical vessel occurring,

with a processing unit for processing the measured values measured bythe sensor,

characterized in that

in at least two gas feed lines there is at least one device for changingthe gas flow through the gas feed line, and each device for changing thegas flow is connected to the processing unit.

The sensor measures measured values correlating with the vibrations ofthe metallurgical vessel occurring, which are processed in theprocessing unit. In this case, quantitative information as to thevibrations of the metallurgical vessel occurring, that is to say forexample as to the frequency and intensity of the vibrations, is obtainedfrom the measured values. The sensor may be fitted on the metallurgicalvessel, for example a converter. According to another embodiment, thesensor is fitted on a part of the plant connected directly or indirectlyto the metallurgical vessel; for example, in the case of a converter, onthe gear mechanism provided for tilting the converter, on thesuspension, or on the foundation on which the converter and associatedparts of the plant, such as the gear mechanism for example, are located.There is at least one sensor, but there may also be a number of sensors.If a number of sensors are present, they may be fitted at one or more ofthe aforementioned locations.

Via the connection to the devices for changing the gas flow, theprocessing unit gives these devices specifications for changing the gasflow. On the basis of the information obtained in the processing unit asto the vibrations of the metallurgical vessel occurring, thesespecifications are devised such that vibrations of the metallurgicalvessel with certain frequencies should be reduced. The specificationsare devised on the basis of expert knowledge stored in the processingunit. This expert knowledge may, for example, be determined and storedduring the commissioning of the metallurgical vessel and consists, forexample, of the natural frequencies of the metallurgical vessel, thenatural frequencies of the parts of the plant connected directly orindirectly to said vessel, or the natural frequency of the overallsystem comprising the metallurgical vessel and parts of the plantconnected directly or indirectly to it. In the case of a converter asthe metallurgical vessel, the overall system essentially comprises thefoundation, gear mechanism, tilting drive, baling ring, suspension andsupport.

The connection of the processing unit to the devices for changing thegas flow may be direct. It may also be indirect; in the case of valvesas devices for changing the gas flow, for example, via a valve unit forcontrolling the valves. The terms connect and connection should beunderstood in this context as meaning that the transmission ofspecifications to the devices for changing the gas flow is possible. Inthe case of an indirect connection, that is to say a connection via afurther device, such as for example a valve unit, this means that thetransmission of specifications from the processing unit takes place viathe further device.

The fact that there is at least one device for changing the gas flow inat least two gas feed lines means that the total amount of gasintroduced per unit of time, the blowing rate, can be kept largelyconstant, since a change at one nozzle can be compensated by an oppositechange at another nozzle.

More preferably, the device for changing the gas flow through the gasfeed line allows changing of the gas flow in stages. It is therefore,for example, a control valve which controls the current through-flow tothe setpoint value.

According to one embodiment, the device for changing the gas flowthrough the gas feed line is a device for continuously changing the gasflow. It is therefore, for example, a control valve which controls thecurrent through-flow to the setpoint value.

The sensor for measured values correlating with the vibrations of themetallurgical vessel occurring is preferably a vibration sensor. Avibration sensor is a device which converts the mechanical vibrationsinto signals that can be used further, which are preferably electricalsignals.

More preferably, the vibration sensor is a torque sensor, anacceleration pickup, a position pickup, a strain gage or a velocitypickup. On account of price and simplicity, acceleration pickups,position pickups and velocity pickups should be preferred.

In FIG. 1, gas, represented by bubbles in the crude steel, is injectedthrough under-bath nozzles 3 a, 3 b, 3 c into a converter 2 filled withliquid crude steel 1. The under-bath nozzles 3 a, 3 b, 3 c arerespectively supplied with gas separately through the gas feed lines 4a, 4 b, 4 c from a gas source line 6 connected to a gas reservoir 5. Thesupply takes place in this case via a valve unit 7. In the valve unit 7,the total amount of gas injected per unit of time can be controlled viavalve 8. In the valve unit 7 in the gas feed lines 4 a and 4 c, thereare also valves 9, 10 for changing the gas flow through the gas feedline. A vibration sensor 11 at the converter 2 sends the vibrationsignals measured by it to a processing unit 12. In this unit,specifications for changing the gas flow for the valves 9, 10 areprepared on the basis of stored expert knowledge and are passed on via aconnecting line to the valve unit 7, and consequently to the valves 9,10. Each of the valves 9, 10 is connected to the processing unit 12 viathe valve unit.

In FIG. 1, an amount of gas represented by 10 bubbles leaves theunder-bath nozzle 3 a per unit of time, an amount of gas represented by10 bubbles leaves the under-bath nozzle 3 b per unit of time, and anamount of gas represented by 10 bubbles leaves the under-bath nozzle 3 cper unit of time. If the processing unit 8 establishes the presence ofan unfavorable frequency A of the vibrations of the converter, it givesthe valves 9, 10 specifications on the basis of which said valves changethe amount of gas injected from the individual underbath nozzles 3 a and3 c per unit of time. The result of the change is represented in FIG. 2,in which an amount of gas represented by 5 bubbles leaves the under-bathnozzle 3 a per unit of time, an amount of gas represented by 10 bubblesleaves the under-bath nozzle 3 b per unit of time and an amount of gasrepresented by 15 bubbles leaves the under-bath nozzle 3 c per unit oftime. The intensity of the frequency A of the vibrations of theconverter, represented in arbitrary units (au), has become lower as aresult of the change.

FIG. 3 shows a schematic drawing of a converter 2, which is fastened ina baling ring 13 via a suspension element 14. A supporting journal ofthe baling ring is connected to a gear mechanism 15, which stands on afoundation 17 via a frame 16. For better overall clarity, furthersuspension elements, parts of the frame as well as further partsnecessary for mounting the baling ring have not been represented. In theconverter itself there are a number of nozzles in the side walls and inthe bottom. The gas feed lines leading to these nozzles are connectedvia a valve unit 7 to the gas source line 6 extending from the gasreservoir 5. Vibration sensors 11 at the converter, baling ring, gearmechanism, frame, suspension element and foundation are connected bylines to the processing unit 12. On the basis of the vibration signalsmeasured by these vibration sensors, the processing unit 12 preparesspecifications for changing the gas flow in gas feed lines leading tothe nozzles. These specifications are passed on to the valve unit 7 viaa connecting line for implementation by valves (not represented) in thegas feed lines.

-   1 crude steel-   2 converter-   3 a, 3 b, 3 c under-bath nozzles-   4 a, 4 b, 4 c gas feed lines-   5 gas reservoir-   6 gas source line-   7 valve unit-   8 valve-   9 valve-   10 valve-   11 vibration sensor-   12 processing unit-   13 baling ring-   14 suspension element-   15 gear mechanism-   16 frame-   17 foundation

1. A method for controlling vibrations of a metallurgical vesseloccurring during the injection of gas into the metallurgical vesselfilled with liquid molten metal, the method comprising: injecting acertain total amount of gas per unit of time into the liquid moltenmetal, wherein the total amount of gas is injected into the liquidmolten metal through a number of individual nozzles in the metallurgicalvessel, and measuring measured values correlating with the vibrations ofthe metallurgical vessel occurring during the injection, wherein whilekeeping the total amount of gas injected per unit of time largelyconstant, the amount of gas injected from individual nozzles per unit oftime is changed in dependence on the measured values that are measuredand correlate with the vibrations of the metallurgical vessel occurring.2. The method according to claim 1, wherein, at least for one of theindividual nozzles, the amount of gas injected from them per unit oftime is changed, at least for a time, in dependence on measured valuescorrelating with the vibrations of the metallurgical vessel occurring.3. The method according to claim 2, wherein the changing of theintensity of at least one measured value correlating with the vibrationsof the metallurgical vessel occurring that is brought about by changingthe amount of gas injected from an individual nozzle per unit of time istraced, and the changing of the amount of gas injected from anindividual nozzle per unit of time is carried out until the at least onemeasured value correlating with the vibrations of the metallurgicalvessel occurring reaches a prescribed value or until the gas flow fromthe nozzle reaches a prescribed maximum or minimum.
 4. The methodaccording to claim 1, wherein the measured values correlating with thevibrations of the metallurgical vessel occurring are filtered anddigitally processed before they are used for changing the amount of gasinjected from the individual nozzles per unit of time.
 5. The methodaccording to claim 1, wherein, when measuring the measured valuescorrelating with the vibrations of the metallurgical vessel occurring,at least one of frequencies and intensities of vibrations aredetermined.
 6. The method according to claim 1, wherein the measuredvalues correlating with the vibrations of the metallurgical vesseloccurring correlate with vibrations of the metallurgical vessel thathave frequencies between 0.1 Hertz and 100 Hertz or between 0.2 Hertzand 20 Hertz.
 7. The method according to claim 1, wherein the measuredvalues, correlating with the vibrations of the metallurgical vesseloccurring, in dependence on which the amount of gas introduced fromindividual nozzles per unit of time is changed correlate with vibrationsof the metallurgical vessel of frequencies that lie between 0.2 Hertzand 20 Hertz.
 8. A device for controlling vibrations of a metallurgicalvessel occurring during the injection of gas into the metallurgicalvessel filled with liquid molten metal and provided with a number ofindividual nozzles for the injection of gas, the individual nozzlesbeing respectively connected to a gas feed line of their own,comprising: at least one sensor for measured values correlating with thevibrations of the metallurgical vessel occurring, a processing unit forprocessing the measured values measured by the sensor, and in at leasttwo gas feed lines there is at least one device for changing the gasflow through the gas feed line, and each device for changing the gasflow is connected to the processing unit.
 9. The device according toclaim 8, wherein the device for changing the gas flow through the gasfeed line allows a continuous changing of the gas flow.
 10. The deviceaccording to claim 8, wherein the device for changing the gas flowthrough the gas feed line is a device for changing the gas flow instages.
 11. The device according to claim 8, wherein the sensor formeasured values correlating with the vibrations of the metallurgicalvessel occurring is a vibration sensor.
 12. The device according toclaim 11, wherein the vibration sensor is a torque measurement, a straingage, a position pickup, a velocity pickup or an acceleration pickup.13. The method according to claim 1, wherein, for two or more of theindividual nozzles, the amount of gas injected from them per unit oftime is changed, at least for a time, in dependence on measured valuescorrelating with the vibrations of the metallurgical vessel occurring.14. A system for controlling vibrations of a metallurgical vesseloccurring during the injection of gas into the metallurgical vesselfilled with liquid molten metal, comprising: a metallurgical vessel, aplurality of individual nozzles for injecting a certain total amount ofgas per unit of time into the liquid molten metal, wherein the system isconfigured to measure values correlating with the vibrations of themetallurgical vessel occurring during the injection, and a control unitwhich, while keeping the total amount of gas injected per unit of timelargely constant, is operable to change the amount of gas injected fromindividual nozzles per unit of time in dependence on the measured valuesthat are measured and correlate with the vibrations of the metallurgicalvessel occurring.
 15. The system according to claim 14, wherein, atleast for one of the individual nozzles, the amount of gas injected fromthem per unit of time is changed, at least for a time, in dependence onmeasured values correlating with the vibrations of the metallurgicalvessel occurring.
 16. The system according to claim 15, wherein thechanging of the intensity of at least one measured value correlatingwith the vibrations of the metallurgical vessel occurring that isbrought about by changing the amount of gas injected from an individualnozzle per unit of time is traced, and the changing of the amount of gasinjected from an individual nozzle per unit of time is carried out untilthe at least one measured value correlating with the vibrations of themetallurgical vessel occurring reaches a prescribed value or until thegas flow from the nozzle reaches a prescribed maximum or minimum. 17.The system according to claim 14, wherein the measured valuescorrelating with the vibrations of the metallurgical vessel occurringare filtered and digitally processed before they are used for changingthe amount of gas injected from the individual nozzles per unit of time.18. The system according to claim 14, wherein, when measuring themeasured values correlating with the vibrations of the metallurgicalvessel occurring, at least one of frequencies and intensities ofvibrations are determined.
 19. The system according to claim 14, whereinthe measured values correlating with the vibrations of the metallurgicalvessel occurring correlate with vibrations of the metallurgical vesselthat have frequencies between 0.1 Hertz and 100 Hertz.
 20. The systemaccording to claim 14, wherein the measured values, correlating with thevibrations of the metallurgical vessel occurring, in dependence on whichthe amount of gas introduced from individual nozzles per unit of time ischanged correlate with vibrations of the metallurgical vessel offrequencies that lie between 0.2 Hertz and 20 Hertz.